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Hearing and Balance - Coggle Diagram
Hearing and Balance
Auditory Pathway
Auditory information is sent to cochlear nucleus in the brainstem
Primary pathway: contralateral
Secondary pathway: ipsilateral
Synapse in Superior Olivary Complex (pons)
Information is relayed to the Inferior Colliculus (midbrain) and Medial Geniculate Body (thalamus)
Information continues to the Primary Auditory Cortex (temporal lobe)
Stapedial Reflex Response
Autonomic and bilateral
Occurs when sounds exceeds 85 dB SPL
Sends information down to stapes
Does not allow any vibration of the ossicles
Tympanic membrane can not vibrate
No movement = no signal transmitted up to auditory nerve
Neurological Auditory/Vestibular Disorders
Auditory Neuropathy
Hearing disorder in which inner ear successfully detects sound but has a problem sending it to the brain
Auditory nerve and/or inner hair cells are impaired
Poor speech perception
Acoustic Neuroma (Vestibular Schwannoma)
Benign growth on CNVIII
Tumor disrupts ability to transmit nerve signals
No standard pattern of symptom development
Hearing loss in one ear
Dizziness/imbalance
Tinnitus
Can grow and press against other cranial nerves which could cause facial weakness/paralysis and swallowing difficulties
Central Auditory Processing Disorder
Deficit in the neural processing of auditory information
Poor performance in auditory discrimination
Caused by brain injury, CVA, degenerative conditions, seizures, age related changes
Difficulty locating sounds, difficulty understanding spoken language, long response time, inconsistent/inappropriate responses, difficulty paying attention, poor performance on speech/language skills
Auditory Agnosias
A group of disorders characterized by a failure to recognize verbal and non verbal sounds
Impairment in sound perception/identification despite intact hearing, cognitive functioning, and language abilities
Verbal is known as word deafness
Non verbal is known as environmental sound agnosia
Meniere's Disease
Disorder of the inner ear that causes severe vertigo, tinnitus, hearing loss, and congestion
Endolymph build up in the labyrinth interferes with balance and hearing signals between inner ear and brain
Benign Proxysmal Positional Vertigo
Sudden sensation that you're spinning
Calcium carbonate crystals in the utricle become dislodged and migrate to one or more semicircular canals
Interferes with normal fluid movement causing inner ear to send false signals to the brain
Cochlea
Scala Vestibuli
Top chamber
Parilymph
Bony
Scala Media
Middle chamber
Endolymph
Lined with Tectorial Membrane
Houses stereosilia
At rest, stereocilia are straight up and down (some K+ and Ca2+ channels are open)
Depolarization: Stereocilia deflects (K+ channels open which triggers depolarization that opens Ca2+ channels which trigger release of neurotransmitters)
Hyperpolarization: Stereocilia displaced (K+ channels are closed, therefore very little K+ and Ca2+ influx, no neurotransmitter signal)
Lined with Basilar Membrane
Houses hair cells
Auditory Signal Transduction
Sounds signal reaches the tympanic membrane
Ossicles begin to vibrate and the stapes pushes against the oval window
Fluid in the cochlea is displaces
Shearing of the stereocilia occurs due to the opposing movements of the basilar membrane and tectorial plate
K+ ions get released
Depolarization of the hair cells occurs
Ca2+ ions flow and attach to the vesicles
Neurotransmitters get released
CNVIII picks up the neural signal
Organ of Corti
Scala Tympani
Bottom chamber
Parilymph
Bony
CNVIII Auditory branch
Tonotopically arranged
Lowest frequencies at apex
Highest frequencies at the base
Vestibular System
Provides information about motion, head position, and spacial orientation
Semi circular canals
Posterior
Shaking head "Yes"
Shaking head "Maybe"
Anterior
Shaking head "Yes"
Shaking head "Maybe"
Horizontal
Shaking head "No"
Ampulla: housed in the Horizontal Duct
Contains vestibular organs
Cupula: contains hair cells that get displaced when fluid movement in the in the semicircular canal displace the cupula
Displacement of hair cells in here trigger action potentials along the vestibular branch of CNVIII
Otolith organs
Utricle
Forward and backward acceleratoin
Saccule
Upward and downward acceleration
Otoconia: crystals that shift in response to movement
Central Vestibular Pathway
Cranial Nerve VIII is processed in Vestibular Nuclei (pons and midbrain)
Info from Vestibular Nuclei is sent to Cerebellum (where balance is processed) and Cranial Nerves involved in eyes/head/torso